Stitch-forming mechanism for sewing machines



Aug. 24, 1943. Y 2,327,817

STITCH-FORMING MECHANISMS FOR-SEWING MACHINES Filed Sept. 3, 1942 NEEDLE THREAD 1 vuQ/wtot/ BOBB/N THREAD BOBB/N THEE/D Patented Aug. 24, 1943 PATENT QFFICE] Miran-FORMING FOR J c SEWING MAcnmEs 1 were "5 Biiflzieiiort, Cdhn as'sighbr'ti)" The Singer Maiiiifactiiring enman-y, Elizabeth;

invention relates to irnprcvementsinjlcchstitch sewing machines andmorepartipulatly te imprcvements in sewing machine loop-talgarand thread-case combinations-designed to cast Jeeps of needle-thread about an interlocking 1 thread housed within thethread-case. I v v y f A v zigzag. ,sewing.;rnachir1 esof; the loch-stitch variety, in which thev-locp-talger iszjpurnaied rearwardl'yhofthe pathpf; needlereciprp cation for clockwise. rotaticn abput an a-is ,snbs1tanti y parallelto thefline of feed -the leadef thebbhbinthread is preferably such that, in the fcrwjard feed of the-work; thestitches forming one side of the line of zigzag stitches are 1055 the type cemmbnly referred to in thetradeas =fperfectfllockstitches and the; stitches iorm-ing theothe'r side (if the line of zigzag stitchesar -of the. type eommb'my referred t0. asv Fhitch 1cck=stitchs. These two types of lock-stitches are iiilly illii's'tratedand at scribed-in the U. patent to I-I'efiilb, Nd. 1,877,757, issued September. 20, 1932; r

When using the 'cbncerned, stitch-forming devices in' a cocpera'ti've relationsuehias shdw'ri in thev accompanyin gi drawing, the ferhiatien of a perfect lock-stitch tends to iihtwist the strands of the readily obtainable standard. left-twist thread, while the formation (if a hitchlc'ck-sti'tch tends to twist ortighten the strands 6f thel'effta twist thread andtto an extent in excess of the untwisting action On the thread caused by th production bf the ii'er ftfldcks'titch. Th formation of stitches in whicli thtstfands '0f the needle-thread are untiivisted is undesirable for the reason that the meme-t rees becdnies'frayed toithe extent that'ithreaks or s not readily formed into aioop by the ascending needle fer seizure by the icon-taker.

In View of the nntwisting df tiineedle-thrad during the fo'rhiatioii' of perfectldck-stitche's; it is desirable i'n'a zigzag leek-stitch machineof the type illustrated in the accompanying drawing to alternately and 'unerring'ly-prcduceperfect lock Stitches arid hitch l6(3k -SIQii/Chs.- The resiilt f this alternate fcrfiiatiri bf perfect and hitch stitches is a twisting o'fthe needle-thread iiia manner such as to be f'avo'i 'aldletothe'staridard left-twist thread: 1 v l It is the priijriary (Jbject et-thepre'sent invention to provide; in a" zigzag-10el stitch sewing=machine; me ns whereby the s'titch fo'rming' mechainisrn Will alternately and ufierrii'igly'efibt thepio'duenon of perfect lock-stitches and hitchldckstitches, the tv'v'p "types of] -stitches :beingwfor-nied On their respective sides I "or y the line: fer; azigzac A. further object of the invention is the provisienof rneanswherebythe lead of thebcbbim thread .canbe varied in accordance \tvith a selected afnplitude of vibration of theneedl'ein order-to "nsure ;the a1ternate production of. perfect lockstitchesandhitchlockstitches.

With the; ab cve and; other, bhjects. View; as will hereinafter app ar, -the inventidn cci'nprises the devices, ccmbinatiens and arrangements of parts herei naft set forth and illustratedin the scqom anymg swing. 6f a preferred er'nbodi mentfioflthinyenticii; from which the several features of th rninvjntioh and the advantages attained thereby Twill be readily Understood by these skilled n the are, I

in accompanyinedrawmg,

en; bf "a ,,smng., machine equipp d ontal aiiis' rotary Inch-taker embodyntidn, L Y ,i'g}; 2 1st vertical 'se'ctioiial Viewftaken ilongitiidiii a'l'fof the sewinginachine. and substantiaily airing theiaikis otriotatio'rr; er the rotaryylobptaker r v t; V n.

ig. 3 yiews mii 1*; ag; 1, my; showing the path 61" the bbbhin readwhen th' sewing mach ne "is yadjnstedpt w: astraightaway seam iristeaddf a'zi'gz'ag sea I 'I f Fig. {1 is a persp'ectiveyiewcf the thread cas',

Fig. 5 is a tObj-plah"VieW of the Werk and a fibrticii cf the rotary lc'op taker with the iisu'al a ert e 'c'f thethroat-plat e hcwn in a dQtand-fda'sh line; showing 'a *Dliira lity- Qt stitches iii' the work and the lead or thefbebbin-thre'ad relative te the needle when the latter hastenetratedthe tvc'rkat the hitch stit'ch side-of the a a ea 1 1 1 j Fig; 6is anew-enter tis Fig. 5, but'shotiing theglead'qffthebdbhin thread relative t0: the ndlwh'n the latter has penetratedthe perfect stitch si es at the zigzag team.

FiJ'Z 'is aviewsimilar tome-.25; biit shewing the preferred lead Uf-fth bebbin-th'iead when the sewing:ihachin'isfadjustedi toaproducea" straightawayiseam. i i 1 Fig: 8: is "a I diagrammatic "view' illustrating: the socalledsfiierfect" lock-stitch; Y i Fig: 9 is a diagrammatic'view illustrating the so-c'alledhitch 1ock=stitchr '7 Referring to the drawing; the present improvement has been embbdiedin:asewingima chine: such .as disclcsedzin-qthe U, S: patent; to

G: Gray; N0; 1,020,039; dated March- 12, 1912. 1

The isewingzmachine has averticaliy reciprocatery and laterally vibratoryjneedle- L andthe machine may be employed for making either zigzag or straightaway stitch seams. The work is supported by a throat-plate 2 provided with the usual feed slots 3 for a work-advancing feeddog 4, said throat-plate also having a needleaperture 5 which in the present case, is elongated transverselyof the line of feed to accommodate lateral vibrations of the needl l.

Cooperating with the needle I, in the formation of lock-stitches, is a rotary loop-taker 6 disposed below the throat-plate 2 and preferably of the rotary hook type. ried by a horizontally disposed loop-taker "shaft 1 having its axis disposed substantially in a verti cal plane containing the normal line of feed of the work, the loop-taker having a cup-shaped l t in its proper position the bottom edge of the flat The loop-taker 6 is car through an elongated aperture 36 provided in the By loosening the screw 35 the fiat platex34.

be shifted to the desired posithread-guide can tion. To assist in maintaining the thread-guide plate 311 rests upon a shoulder 31 formed on the body provided at the outer edge of .itsvperiphery I with a needle-thread loop-seizing beak 8 anda upper edge of that guide .defining one side of the usual guideway in which slides the regular ijlatchingdevice 24.

having the thread-guide adjustably mounted is The primary advantage of that the lead of the bobbin-thread can be regulat ed in accordance with selected amplitudes of loop-discharging tail 9 adjacent and directed-ope;

positely to the beak 8. Formed in the cupshaped body of the logipPtakr Bis an internal raceway Ill of which the-outer-side wall is pro vided by a detachable gib' l I securedto the looptaker body by screws l2; i 1

Disposed within the cup-shaped hook-body is a two-part threadc ase (Fig.2) comprising a base-section I3 and" a telescopically arranged cap-section l4; The base-section I3 'is cupshaped and is'formed externally adjacent its rim with the usual peripheral bearing rib 'Whi0h is journaled in the racewayfll llprovidedfin the hook-body; At the'outer'edgeof the, rimof the .base section l3 thereis. provided a flange 16 having in its outer or front face a rotation-re straining notch l1 adapted to) beentered bythe tongue of the usual rotatior 'restraininfg. bar (not shown) common toQrotarylock stitchfs ewing m a chines. Adjacent the rotation-restraining notch I! the flange I5 is formed with a bobbin thread guiding slot 18 which is separate and. distinct from the rotation-restraining notch I' l. Extending axially from the bottom wall oifv the base-section I3 is a cylindrical bobbin-supporting post l9 recessed at 20 to provide a head 2l. Slidably mounted on the bobbinsup'p'or tirigvv post lfi'isa tubular arbor 22 extending-inwardly from the cap-section M, which tubular, arbor'freely re- .ceives the regular thread-carryingbobbin-mam ber 23 (Fig.

2). The cap-section l4 isse'cured improper position upon.theJbobbin-supporting post I9 by a latching device 24, the constructive features of which are fully disclosed inthefU. S, Patent. No. 1,995,278, issued to C. A, Kessler; on March 19, 1935. i i 7 As clearly shown in Fig.- 4,;the-cap-section Hi includes a thin vertical circular faoe-rportion .25 terminating at its periphery ina horizontal cylindrical skirt-portion 26 nctched, as at 21, and grooved, as at 28, to receive and guide the-bobbin-thread 29 which. leads from the bobbinmember 23 across the outer, surface of thefaceportion of the thread-lease. To-apply-the necessary tension on'the bobbin-thread 29 there is secured on the face-portion 25 a tensionspring 30 having at its .free end the inturned lip notched at 3! to receiveand 'gui'de'the'bobbinthread 29. The tensionapplied on. the bobbinthread by the springtncan be regulated by the screw 32 which is threaded'into the face-portion 2 f thecap-sec'tioriM." 1

"Cooperating with the I notched tension-spring 30 in properly leading the"bobbin-thread 29 rela-' tiveto'the needle l is a th're'ad-guide'in' the form of a thread-delivery slot 33 having a closed end vibrationof the needle in order to insure that the needle in its successive work-penetrations willpass-bn-the "opposite sides of 'the bobbinthreadgftherebyto" effect the desired alternate production of perfect lock-stitches 'and hitch lock-stitches. It will be' understood that as' the amplitude "of the needle-vibration isreduced the lead of the bobbin-thread, such that perfect lock-stitches and hitch lOck-Stitchesare alternately forni ed, becomesmore critical. By mount-- ing the'thread guide so that'the thread-slot 3 3 canbe'shifted transversely of the seam linethe' required degree-of-accuracy in the lead of the bobbin-thread can be readily obtained. While I have shown the thread-slot 33 as havingan open .end' to facilitate threadingQit will be appreelated that thethreadfslot may be formed as an aperture without in any way affecting its action.

"In" operation; when the bobbin thread 29 passes from the-notch Si in the tension-spring Bii'ftothe' thread-slot 33 thence through the rotation-restraining notch 11 to the work, thelead of the bobbin-thread is'such that when; the' needle I is descending through the work at the left-hand side ofthe'zi'gzag' seam (i. eflalong the line a, Fig. 6),theneedle passes thegbobbinf threadl 29 On the left-hand side of, the latter, as

shown in Fig.6." The re'sultiof this relation of bobbin-threadjlead totheneedle, when concatenating the needle-thread and the bobbin-thread to'produce'a perfect lock-stitch, shown diagrammatically in Fig. 8.1 jWhen'the needlel descends throughthe I work 'at theright-hand size of the zigzag seam (i. e., along 'the;linenb, Fig. 5) the needle passes the bobbin-thread 29 on the right-hand side of the lattenas shown in Fig. 5. The resultof this relation of bobbin-threadl-leadto the needle, when concatenating theneedle-thread and the bobbin-thread to produce a .lockestitch, is' the formation of a hitch lock stitch,lsuch as shown in Fig.1 When the needle and loop-taker co} I operate in; the manner shown in the drawing, the

and-break or fail to bow out and form the usual;

' thread-loop for seizure by the advancing beakof therloop-taker. taker cooperate; towform lock stitches in which the needle-thread. makes a series of. knots on half-hitches around thebQbbin-thread, see 9,

lock-stitch, is the formation, of a When thefneedle and loop the concatenation of the two threads is such as to tighten the twist of the conventional lefttwist thread. It is desirable that the inherenttwist of the thread with which the sewing is done be conserved so that the normal characteristics of the thread will not be lost. With these facts in mind, it will be appreciated that, if in the type or" machine illustrated, the formation of a periect-lock-stitch tends to untwist a conventional left-twist thread and the formation of a hitch lock-stitch tends to tighten a left-twist thread, it is necessary to alternately produce perfect lock-stitches and hitch lock-stitches in order not to affect the normal twist of the thread.

It will be understood fromthe foregoing that I have provided simple means for insuring the alternate production of perfect lock-stitches and hitch lock-stitches. Furthermore, provision has been made so that, as the amplitude of vibration of the needle is adjusted, the lead of the bobbinthread can be accurately controlled in accordance with the selected amplitudes of vibration, whereby the alternate formation of perfect lockstitches and hitch lock-stitches is insured.

It is desirable in zigzag sewing machines that provision be made whereby the amplitude of needle-vibration can be reduced to zero to enable the machine to produce straightaway seams. To provide for this contingency the thread-case I4 is formed with the usual bobbin-thread guiding slot I8 into which the bobbin-thread Z9 is placed (Fig. 3) when the sewing machine is adjusted to produce a straightaway seam. When the bobbinthread is directed to the work by the threadguiding slot It, the lead of the bobbin-thread is such that the needle passes the bobbin-thread on the right-hand side of thelatter. By so doing hitch lock-stitches are continuously formed. Inasmuch as hitch lock-stitches favorably twist the conventional left-twist thread, when the stitches l Having thus set forth the nature of the invention, whatI claim herein is:

1. In a zigzag sewing machine, an endwise reciprocatory thread-carrying needle having laterally vibratory movements of variable amplitude, a circularly moving loop-taker cooperating with said needle in the formation of lock-stitches, a thread-case for an interlocking bobbin-thread disposed within said loop-taker and restrained against movement with said loop-taker, a threadthread-case for an interlocking bobbin-thread disposed within said loop-taker and restrainedally vibratory movements of variable amplitude,

a feeding mechanism, a circular moving looptaker movable in a plane transversely of the normal line of feed and cooperating with said needle in the formation of lock-stitches, a thread-case for an interlocking bobbin-thread disposed within said loop-taker and restrained against movement with said loop-taker, a thread-guide for directing the interlocking-bobbin-thread in a pre determnied relation with respect to said needle, and means providing for variation of the position of said thread-guide transversely of the nor mal line of feed in accordance with selected amplitudes of vibration of said needle.

4. In a zigzag sewing machine, an endwise reciprocatory thread-carrying needle having laterally vibratory movementsof variable amplitude, a circularly moving loop-taker cooperating with said needle in the formation of lock-stitches, a thread-case for an interlocking bobbin-thread disposed within said loop-taker and restrained against movement with said loop-taker, said thread-case having a face-portion, a threadguide for directing the interlocking bobbin-thread in a predetermined relation with respect to said needle, said thread-guide comprising a plate secured fiat against the face-portion of said threadcase and having a thread-directing opening therein, and means securing said plate to said face-portion with capacity for varying the position of the thread-directing opening in accordance with selected amplitudes of vibration of said needle.

5. In a zigzag sewing machine, an endwise reciprocatory thread-carrying needle having laterally vibratory movements of variable amplitude, at circularly moving loop-taker cooperating with said needle in the formation of lock-stitches, a thread-case for an interlocking bobbin-thread disposed within said loop-taker and restrained against movement with said loop-taker, said thread-case having a face-portion, a thread-guide for directing the interlocking bobbin-thread in a predetermined relation with respect to said needle, said thread-guide comprising a plate secured flat against the face-portion of said threadcase and having formed therein a thread-directing opening and an elongated aperture, and a screw extending through said elongated aperture and threaded into the face-portion of said thread-case. i

- FRANK PARRY. 

